This invention relates to liquid-vapour separators of the capillary separation type, and to propellant tanks for space vehicles incorporating such liquid-vapour separators.
Known propellant tanks for space vehicles make use of liquid-vapour separators of the capillary separation type in which surface tension forces inhibit vapour flow whilst preferentially allowing liquid flow through fine passages. Fine mesh with micron size apertures produces the required surface tension forces to separate liquid and vapour, and this is incorporated in a liquid collecting gallery within an aft section of the tank through which liquid propellant is extracted. Additionally, an internal bulkhead may be provided which divides the tank into forward and aft sections and incorporates fine mesh that allows the flow of liquid from the forward to the aft section where the liquid is trapped in contact with the collecting gallery. The bulkhead also incorporates a vent stack with fine apertures which vent vapour from the aft section to the forward section as the aft section fills with liquid from the forward section. This design of tank involves a complex assembly to which the fine mesh is supported.
A propellant tank for a space vehicle is disclosed in GB 1568275 which makes use of a liquid separator comprising a plurality of annular discs compressed in a stack with radially directed recesses formed in their cooperating surfaces so as to define fine passages through which liquid flows. A number of such stacks are interconnected by pipework and located around the periphery of the tank to extract liquid from it. This type of liquid-vapour separator is more robust and easier to assemble and maintain compared with mesh-type liquid-vapour separators. However, the tank of GB 1568275 does not incorporate a bulkhead that divides the tank into sections, with one section trapping liquid in contact with the liquid-vapour separator.